1. Field of the Invention
The present invention relates to an apparatus for controlling the timing of igniting air-fuel mixture in automobile engines.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 64-77753 describes a typical electronic spark advance apparatus. The apparatus controls the flow of primary current in an ignition coil based on signals from a control circuit. The control circuit sets the optimum current flow time in correspondence with the operating state of the engine. This determines the optimum ignition timing.
The speed of the engine is extremely slow when the engine is being started or when the engine is about to stall. This leads to current flow that continues for a long period of time. In such case, a current breaker mechanism breaks the flow of the primary current when the current keeps flowing for a predetermined period of time. The breaker mechanism prevents the primary current from being locked in a continuously flowing state. This prevents heating of the ignition coil and power transistors of ignitors.
However, the length of the predetermined time, or current allowance time, is the same regardless of whether the engine is being started or whether the engine is already running. Furthermore, low temperatures degrade the starting performance of the engine and delays increase in the engine speed. Thus, if the engine is being started under low temperature conditions, the current allowance time causes ignition at an undesirable timing. This further degrades the starting performance of the engine.